21,131 research outputs found
Theoretical Aspects of Blunt Body Magnetoaerodynamics
Supersonic magnetoaerodynamic flow about blunt body with self contained magnetic field sourc
Estimation of Kalman filter model parameters from an ensemble of tests
A methodology for estimating initial mean and covariance parameters in a Kalman filter model from an ensemble of nonidentical tests is presented. In addition, the problem of estimating time constants and process noise levels is addressed. Practical problems such as developing and validating inertial instrument error models from laboratory test data or developing error models of individual phases of a test are generally considered
Practical applications of interactive voice technologies: Some accomplishments and prospects
A technology assessment of the application of computers and electronics to complex systems is presented. Three existing systems which utilize voice technology (speech recognition and speech generation) are described. Future directions in voice technology are also described
Antiquark nuggets as dark matter: New constraints and detection prospects
Current evidence for dark matter in the universe does not exclude heavy
composite nuclear-density objects consisting of bound quarks or antiquarks over
a significant range of masses. Here we analyze one such proposed scenario,
which hypothesizes antiquark nuggets with a range of log10(B) = 24-30 with
specific predictions for spectral emissivity via interactions with normal
matter. We find that, if these objects make up the majority of the dark matter
density in the solar neighborhood, their radiation efficiency in solids is
marginally constrained, due to limits from the total geothermal energy budget
of the Earth. At allowed radiation efficiencies, the number density of such
objects can be constrained to be well below dark matter densities by existing
radio data over a mass range currently not restricted by other methods.Comment: 6 pages, 3 figures, revised references; submitted to PR
Cosmic-ray electron injection from the ionization of nuclei
We show that the secondary electrons ejected from the ionization of heavy
ions can be injected into the acceleration process that occurs at supernova
remnant shocks. This electron injection mechanism works since ions are ionized
during the acceleration when they move already with relativistic speed, just
like ejected electrons do. Using the abundances of heavy nuclei measured in
cosmic rays at Earth, we estimate the electron/proton ratio at the source to be
~10^-4, big enough to account for the nonthermal synchrotron emission observed
in young SNRs. We also show that the ionization process can limit the maximum
energy that heavy ions can reach.Comment: 4 pages, 1 figure, accepted for publication in Physical Review
Letter
The Cauchy convergence of T and P-approximant templates for test-mass Kerr binary systems
In this work we examine the Cauchy convergence of both post-Newtonian
(T-approximant) and re-summed post-Newtonian (P-approximant) templates for the
case of a test-mass orbiting a Kerr black hole along a circular equatorial
orbit. The Cauchy criterion demands that the inner product between the and
order approximation approaches unity, as we increase the order of
approximation. In previous works, it has been shown that we achieve greater
fitting factors and better parameter estimation using the P-approximant
templates for both Schwarzschild and Kerr black holes. In this work, we show
that the P-approximant templates also display a faster Cauchy convergence
making them a superior template to the standard post-Newtonian templates.Comment: 5 pages, Replaced with shortened published versio
- …